I have an Ampeg j20, which is a 6g3 based circuit, I have modded it to be closer to the original fender 6g3 circuit. The amp had an Ampeg branded 12" alnico in it when I got the amp 10 years ago, I found the high end to be to harsh and the low end to be very fluby any time the amp got tuned up past 4. It currently has a celestion greenback which is okay but a little to miss focused for my taste. I mostly use this amp for blues and country. I love the John Mayer, SRV , and hendrix type tones for blues, and for country the chris stapleton tones, or early stuff like Waylon Jennings in Merle Haggard. I'm considering the blackhawk, and the WG12A.
Blackhawk would be perfection.
The G12A MIGHT still be just a tad bright for you ... but also a very good choice, kinda a little of the original Ampeg tone mixed with bright blackface Fender tone.